U.S. Pat. No. 3,235,401 describes a device of this type with which the material web to be coated is deflected onto a transfer roller from a guide roll of an applicator. The transfer roller drags spreadable dyestuff from a dyestuff bath [tray or trough] and entrains it in excess onto the web. To strip off a part of the spreadable dyestuff applied in excess, the web following the transfer roller is guided over a driven roll squeegee rod [roll doctor rod] provided with a wire wrapping. At a distance from the roll squeegee rod there follows a counter roller about which the web is deflected and whereby, in the looped region of the controllers, an air blade is arranged which strips the surplus spreadable colorant off to the desired coating weight.
It is a disadvantage of known air blade machines, especially with large machine widths, that a closed and uniform coating of the material web can only be produced at limited production speeds (less than 500 m/min).